Office attached to house, few questions

[Penance]

Been to look at a job at a mates house today. They are having a two storey extension to side of house and a single storey extension at the rear of the two storey.
Single storey will be an office for 3 employees of his business.
There will be a single door access from rear of house to office but this will not be used by the employees.
Will the work carried out on the office be notifiable?

Also they want a sub main in the office so that if anything trips the employees will not need to access a cu in the house. I am thinking of splitting the tails to a single mcb then running swa to the cu in office. Is that ok without rcd protection at house end?

 

[Electricalserv]

Been to look at a job at a mates house today. They are having a two storey extension to side of house and a single storey extension at the rear of the two storey.
Single storey will be an office for 3 employees of his business.
There will be a single door access from rear of house to office but this will not be used by the employees.
Will the work carried out on the office be notifiable?

Also they want a sub main in the office so that if anything trips the employees will not need to access a cu in the house. I am thinking of splitting the tails to a single mcb then running swa to the cu in office. Is that ok without rcd protection at house end?

If the service head from the house is supplying the office aswell. Its notifiable.

 

[londonlec]

If you use armoured then you won't need to worry about RCD protection for cables buried less than 50mm.

Don't use an MCB, instead use a fuse, maybe of BS88 or BS1361.

This will provide discrimination between the intake, and the consumer unit within the new office.

 

[malcolmsanford]

If though the house is TT the chances are you will have to protected the SWA with a 100mA RCD, if it is TT you may be lucky and have a front end one already installed and then 30mA the CU in the office.

 

[Penance]

Thought it would be notifiable, thanks for confirmation.

Good call on fuse, hadn't thought of that.

 

[Guest123]

Been to look at a job at a mates house today. They are having a two storey extension to side of house and a single storey extension at the rear of the two storey.
Single storey will be an office for 3 employees of his business.
There will be a single door access from rear of house to office but this will not be used by the employees.
Will the work carried out on the office be notifiable? Yes as it shares the same supply as the house.

Also they want a sub main in the office so that if anything trips the employees will not need to access a cu in the house. I am thinking of splitting the tails to a single mcb then running swa to the cu in office. Is that ok without rcd protection at house end? Dependant on earthing system.

Sounds like a lot of additional works, is the existing electrical supply sufficient to be added to??

 

[Penance]

Malcolm, not TT but TNCS.
Will be doing cu change as first priority, currently old wylex with mcb.
Couldn't find any service bonding, water will be easy to sort but gas is in outside meter box and pipe enters below floor level. Ok to bond in outside box?

 

[malcolmsanford]

Yes reg 544.1.2 does say where practable so to me that gives us as electricians a bit of leeway and as long as IMO you do it before a branch and on the solid pipe, they are the important part of the reg.

 

[Penance]

Lenny, I believe so but do need to check. Today was just a quick visit for a chat about proposed work.
Service fuse said 80a but didn't pop it out to check.
The office is small, will be around 10 dso's for computer/laptop use. A small kitchen area with toaster, kettle and microwave and a washroom needing 1 light and a fan.
The office is for accountants so I don't imagine a heavy demand.

Obviously a lot needs clarification before any work commences.

 

[Penance]

Thanks Malcolm, thought it would be ok but always good to get advice and opinions.